SETI public: Giant black holes wandering the Universe

• Previous message: LARRY KLAES: "SETI public: A bunch of recent relevant papers"

Paper: astro-ph/0512073
Date: Fri, 2 Dec 2005 21:46:44 GMT (309kb)

Title: The Effect of Gravitational Recoil on Black Holes Forming in a
Hierarchical Universe

Authors: N. I. Libeskind, S. Cole, C. S. Frenk, J. C. Helly

Comments: 12 pages, 7 figures, Submitted to MNRAS
\\
Galactic bulges are known to harbour central black holes whose mass is
tightly correlated with the stellar mass and velocity dispersion of the
bulge.
In a hierarchical universe, mergers of subgalactic units are accompanied by
the
amalgamation of bulges and the likely coalescence of galactocentric black
holes. In these mergers, the beaming of gravitational radiation during the
plunge phase of the black hole collision can impart a linear momentum kick
or
``gravitational recoil'' to the remnant. If large enough, this kick will
eject
the remnant from the galaxy and populate intergalactic space with wandering
black holes. Using a semi-analytic model of galaxy formation, we investigate
the effect of black hole ejections on the scatter in the relation between
black
hole and bulge mass. We find that although not the dominant source of the
measured scatter, they do make a significant contribution and may be used to
set a constraint, v_kick<500 km/s, on the typical kick velocity, in
agreement
with values found from general relativistic calculations. Even for the more
modest kick velocities implied by these calculations, we find that a
substantial number of central black holes are ejected from the progenitors
of
present day galaxies, giving rise to a population of wandering intrahalo and
intergalactic black holes whose distribution we investigate in
high-resolution
N-body simulations of Milk-Way mass halos. We find that intergalactic black
holes make up only ~2-3% of the total galactic black hole mass but, within a
halo, wandering black holes can contribute up to about half of the total
black
hole mass orbiting the central galaxy. Intrahalo black holes offer a natural
explanation for the compact X-ray sources often seen near the centres of
galaxies and for the hyperluminous non-central X-ray source in M82.

\\ ( http://arXiv.org/abs/astro-ph/0512073 , 309kb)

Paper: astro-ph/0512123
Date: Mon, 5 Dec 2005 20:41:27 GMT (913kb)

Title: The Role of Primordial Kicks on Black Hole Merger Rates

Authors: Miroslav Micic, Tom Abel and Steinn Sigurdsson

Comments: 12 pages, 9 figures, submitted to MNRAS

Journal-ref: proceedings of 22nd Texas Symposium on Relativistic
Astrophysics,
Stanford University, December 13-17, 2004
\\
Primordial stars are likely to be very massive $\geq30\Msun$, form in
isolation, and will likely leave black holes as remnants in the centers of
their host dark matter halos in the mass range
$10^{6}-10^{10}\Ms$. Such early black holes, at redshifts z$\gtsim10$, could
be the seed black holes for the many supermassive black holes found in
galaxies
in the local universe. If they exist, their mergers with nearby supermassive
black holes may be a prime signal for long wavelength gravitational wave
detectors. We simulate formation of black holes in the center of high
redshift
dark matter halos and explore implications of initial natal kick velocities
conjectured by some formation models. The central concentration of early
black
holes in present day galaxies is reduced if they are born even with moderate
kicks of tens of km/s. The modest kicks allow the black holes to leave their
parent halo, which consequently leads to dynamical friction being less
effective on the lower mass black holes as compared to those still embedded
in
their parent halos. Therefore, merger rates may be reduced by more than an
order of magnitude. Using analytical and illustrative cosmological N--body
simulations we quantify the role of natal kicks of black holes formed from
massive metal free stars on their merger rates with supermassive black holes
in
present day galaxies. Our results also apply to black holes ejected by the
gravitational slingshot mechanism.

\\ ( http://arXiv.org/abs/astro-ph/0512123 , 913kb)

Paper: astro-ph/0511397
replaced with revised version Mon, 5 Dec 2005 12:21:20 GMT (464kb)

Title: The ecology of star clusters and intermediate mass black holes in the
Galactic bulge

Authors: Simon Portegies Zwart (UvA), Holger Baumgardt (Bonn), Stephen L. W.
McMillan (Drexel), Junichiro Makino (tokyo), Piet Hut (IAS), Toshi Ebisuzaki
(RIKEN)

Comments: 26 pages, ApJ in press.

Old title: The Galactic center welcomes black hole immigrants

We simulate the inner 100pc of the Milky-Way Galaxy to study the formation
and evolution of the population of star clusters and intermediate mass black
holes. For this study we perform extensive direct N-body simulations of the
star clusters which reside in the bulge, and of the inner few tenth of
parsecs of the super massive black hole in the Galactic center. In our
N-body simulations the dynamical friction of the star cluster in the tidal
field of the bulge are taken into account via (semi)analytic soluations. The
N-body calculations are used to calibrate a (semi)analytic model of the
formation and evolution of the bulge. We find that about 10% of the clusters
born within 100pc of the Galactic center undergo core collapse during their
inward migration and form intermediate-mass black holes (IMBHs) via runaway
stellar merging. After the clusters dissolve, these IMBHs continue their
inward drift, carrying a few of the most massive stars with them. We predict
that region within about 10 parsec of the SMBH is populated by about 50IMBHs
of some 1000Msun. Several of these are expected to be accompanied still by
some of the most massive stars from the star cluster. We also find that
within a few milliparsec of the SMBH there is a steady population of several
IMBHs. This population drives the merger rate between IMBHs and the SMBH at
a rate of about one per 10Myr, sufficient to build the accumulate majority
of mass of the SMBH. Mergers of IMBHs with SMBHs throughout the universe are
detectable by LISA, at a rate of about two per week.

\\ ( http://arXiv.org/abs/astro-ph/0511397 , 464kb)

• Previous message: LARRY KLAES: "SETI public: A bunch of recent relevant papers"

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